What is SPACE ENERGY (Space-based Solar Power)?

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Space-based solar power (SBSP) is the concept of collecting free solar energy in space with solar power satellites, and beaming it wirelessly back to Earth for distribution. The main benefit is that it can reliably provide clean energy 24/7.

Limitations of ground-based solar power

In recent years solar energy has become more affordable and efficient, resulting in widespread adoption at record levels of annual deployment capacity worldwide. However, inherent limitations persist: 

• Solar panels only function during daylight hours
• The energy density of solar is very low
• Cloud cover intermittently hinders performance
• the atmosphere absorbs a significant portion of sunlight before it reaches the Earth's surface
• Needs to backed up by more reliable and dispatchable sources such as hydro, nuclear and fossil-fuels, and (to a limited extent) storage solutions such as batteries 
• Limited by how quickly it can be scaled up across the globe due to intermittency of supply, pressures on land-use and concerns about energy security

The combination of energy storage technologies with solar can address some of these limitations to some extent, but the existing storage technologies are limited in scalability by their associated economic and environmental costs. Therefore there remain great challenges with fully decarbonising energy systems at the same time as meeting the ever-growing need for renewable electricity globally in a rapid, affordable manner, while maintaining reliability and security.

Why should we consider space-based solar power? 

While the idea of SBSP has existed for over 50 years, it has gained renewed importance in recent years in Europe and worldwide due to the urgent need for clean, affordable, scalable and secure energy sources to support decarbonisation for mitigating global warming. Numerous studies have repeatedly shown that SBSP, used effectively in complement with other clean energy sources such as ground-solar and wind, can help accelerate the decarbonisation of societies. SBSP could therefore ultimately provide the elusive solution to the 'Energy Trilemma' of sustainability, affordability and security.

Main challenges of realising space-based solar power

SBSP relies on established technological principles and known physics, requiring no groundbreaking discoveries. However, the primary challenge lies in the scale of the required structures both in space and on Earth. To serve large-scale users and to supply the grid, power plants in orbit producing hundreds of megawatts to gigawatts of power are required to replace existing non-clean sources such as coal and gas power stations. 

To gather such levels of solar power, even in orbit where the Sun is more intense, would require solar farms square kilometres in area, with  ground-based receiver stations a few kilometres across. This is very much larger than any structure that has been assembled in space today. The construction of such large structures in space  would require affordable and regular launches to place the necessary hardware in orbit, as well as autonomous robotic in-space assembly systems. Fortunately, such systems are in development today and will soon be in regular use.

How solar energy can be beamed to Earth

The generated power would be transmitted wirelessly through very large, modular transmitters to the receiving antennas on the ground (referred to as rectennas), typically through the use of safe, low-intensity radio frequencies, similar to those used for Wifi, mobile phones and satellite communications. The chosen frequency would allow the beam to reach the receivers with almost no loss through the atmosphere, whatever the weather conditions, thus providing a continuous and reliable source of clean power 24/7. Wireless power transmission using radio frequencies, itself not a new technology, has been repeatedly demonstrated in the last decades at power levels up to tens of kilowatts and distances up to 1.8 kilometres.

How close are we to realising space-based solar power?

Previously, despite its attractive characteristics as a potential global energy source, high launch costs from expendable launchers made SBSP economically unfeasible compared to terrestrial solutions. However, now with the advances in wireless power transmission, mass-production of spacecraft, and with the proof that reusable rockets can dramatically reduce launch costs – with the potential to lower costs even further through upcoming heavy-left launch vehicles like Starship – the construction of dedicated space-based solar power satellites is finally approaching economic viability.